US2794886A - Electric circuit breakers of the air or gas-blast type - Google Patents

Description

June 4, 1957 A. ROXBURGH ETAL 2,794,886

ELECTRIC CIRCUIT BREAKERS OF THE AIR OR GAS-BLAST TYPE Filed Feb. 21, 1955 2 Sheets-Sheet 1 Q TORNE/ June 4, 1957 A. ROXBURGH EIAL 2,794,886

Filed Feb. 21, 1955 ELECTRIC CIRCUIT BREAKERS OF THE AIR OR GAS-BLAST TYPE 2 Sheets-Sheet 2 28A 28 35A 1L 55s SIA 30 2 3H;

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v 2 48 INVENTORJ United States Patent ELECTRIC CIRCUIT BREAKERS OF THE AIR OR GAS-BLAST TYPE Albert Roxburgh, London, and Albert Leigh, Kenton, England, assignors to The British Thomson-Houston Company Limited, a British company Application February 21, 1955, Serial No. 489,564 Claims priority, application Great Britain March 2, 1954 Claims. (Cl. 200-148) This invention relates to electric circuit interrupters of the. air or gas-blast type, and particularly to such circuit interrupter-s of the kind wherein a resistor is connected in parallel with the circuit interrupting contact gap or gaps for controlling the recovery voltage rise or otherwise improving the circuit interrupting characteristics of the interrupter.

In a common arrangement of circuit interrupter of the kind above referredto, the main or circuit interrupting contacts are mounted within a contact chamber and biased to'the closed position, being opened by the application of airpre'ssiire to said contact chamber; the circuit interrupterjin'cludes, 'in series with the main contacts, isolating contacts, usually operating in free air, whereby to main tainthe circuitopen after reclosure of said circuit interruptingicoiifactswhen the air pressure is removed from the contact chamber. The resistor. has usually been connected permanently in parallel with the circuit interrupting contacts so that the isolating contacts referred to are required to interrupt the residual current flowing through the resistor after interruption of the are drawn upon opening of the main contacts.

According to the present invention, in an electric circuit interrupter. of the kind referred to a gap is included in series with the.resistor, the electrodes of said gap and the resistor'b'eing thus connected in parallel with the main or circuit interrupting contacts, said gap being arranged to breakdown and permit passage of current through said resistor when the main contacts, are opened, and means are provided for the application of air or gas pressure to said series gap whereby to quench the arc in the latter and terminate the flow of current through the series resistor. In carrying out the invention, means may be provided for applying the air or gas pressure to the series gap with a time delay after opening of the main contacts.

The invention is eminently, although not exclusively, applicable in circuit interrupters in which the separation of the main contacts is efiected by the application of the air or gas pressure to the contact chamber.

Preferably, the electrodes referred to are housed fixedly with respect to one another in an auxiliary chamber to which the air or gas under pressure employed for extinguishing the arc between the main contacts, is adapted to be applied under control of time delay means in response to the application of the air or gas pressure to the main contact chamber.

In preferred arrangements according to the invention valve means responsive to the air or gas pressure applied to the main contact chamber are arranged so as to close the air or gas discharge passages from said chamber with a time delay after the application of said air pressure to the main contact chamber, and the auxiliary chamber housing the series electrodes is connected by means of a passage conduit or the like with said contact chamber on the downstream side of the main contacts, whereby the closing of said discharge'passages will cause the pressure in the contact chamber and in said auxiliary chamber to rise to that on the upstream side of the main contacts.

Patented June 4, 1957 ICC 2 n This pressure will then be sufficient to extinguish the are between the electrodes and so interrupt the resistor current.

In carrying out the invention the circuit interrupter may or may not include isolating contacts as part of the interrupter itself, since there is no residual current to be interrupted after the electrode gap has extinguished the resistor current, and therefore the open circuit conditions are maintained for so long as the main contacts are open. In cases in which the main contacts are separated by the air or gas pressure applied to the contact chamber the open circuit conditions can be maintained by maintenance of said pressure, preferably by closing discharge passages from said chamber by valve means as hereinbefore set forth. In cases in which isolating contacts are provided.

as part of the circuit interrupter itself means may or may not be provided whereby after opening of the isolating contacts the air or gas pressure will be released from the contact chamber and the auxiliary chamber and reclosure of the main contacts thereby effected. The opening of the isolating contacts may, for example be effected by the usual means so as to occur after extinction of the current in the resistor.

According to a further feature of the invention, the electrodes are positioned within a space subject to reduction of pressure due to flow of the air or gas from the main contact chamber whereby to facilitate breakdown of the gap between said electrodes. Conveniently, the electrodes may be positioned within an auxiliary chamber communicating with a point in the main contact chamber adjacent a discharge port or ports in said main chamber.

Reference will now be made by way of example to the accompanying drawings, in which:

Fig. l is a sectional elevation showing a preferred embodiment of the invention,

Fig. 2 is an outline elevation illustrating one application of the arrangement of Fig. l in combination with an isolating switch means, and

Fig. 3 is an outline elevation showing part of a circuit breaker comprising a duplication of the contact arrangement of Fig. 1.

In Fig. l the circuit breaker includes a main contact chamber which is of the otherwise well known type comprising a horizontal tubular insulating member 1 extending from a conductive assembly 2 mounted on a tubular supporting insulator, 3, the lower end of which is secured to a member 4 which in turn is suitably mounted on a main framework or base (not shown) for the circuit breaker. The tubular member 1 carries at its free end a contact and line terminal unit or assembly 5. The assembly 5 comprises a metal casing 6 having an end wall 7 which closes the adjacent end of the tube 1, the assembly 5 being secured to the member 1 such as by a metal ring 8 of the usual construction secured to the wall 7. The other end of the member 1 is secured .to the metal assembly 2 by means of a similar ring 9.

The wall 7 is formed with a cylinder 10 which extends inwardly and coaxially of the insulating member 1 and a tubular moving contact member 11 extends through an aperture at 12 in the wall 7. Contact 11 includes a flange 13 which forms a piston working within the cylinder 10 and operable by air pressure in said cylinder. The contact 11 is adapted to engage at its inner end with a fixed rod 14 which extends from the conductive assembly 2, being mounted therein by means of a metal tube 15 which is secured, such as by welding, to an end-plate 16 closing the assembly 2.

The various parts of the circuit breaker are shown in Fig. 1 at an intermediate stage during the interruption of the current as will hereinafter be described.

The metal casing 6 is formed as a cylinder in which is movable a piston 17, this piston being biased by means of a compression spring 18 into engagement with the adjacent end of the tubular moving contact 11 so as in the normal condition of the switch parts to hold the latter in contact with the end of the fixed contact 14. The piston 17 is provided with vents such as 19 whereby free movement of said piston is permitted, said vents equalising the pressure on the two sides of the piston whereby the latter will not be responsive to the pressure conditions within the casing 6.

The space within the cylinder 12 in rear of the piston 13 is vented to atmosphere by a passage 20. The casing 6 includes a further cylindrical portion 21 provided with a plurality of outlet ports such as 22, which ports are however normally closed by means of a piston 23 which is movable in the cylinder 21 and is biased upwardly by means of a compression spring 24. The upward movement of the piston 23 is limited by a shoulder at 25 to a position wherein said piston closes the ports 22. The outer end of the cylinder 21 is connected by a pipe 26 with a port 27 in the cylinder 10, the arrangement being such that whereas in the illustrated open position of the contact 11 the piston 13 is to the left of said port, in the normal circuit-closed position of said contact 11 the port 27 will be closed by the piston 13 against flow of air from the member 1 into the pipe 26.

The resistor in this embodiment of the invention comprises a metallic element 28 housed within a tubular insulating casing 29 conveniently supported as shown with its axis parallel with that of the member 1. The casing 28 is mounted by means of a conducting member 30 which serves to connect one end of the resistor with the assembly 2 and thereby with the fixed contact 14, and by means of a conductive member 31 secured to the casing 6. The member 31 constitutes a fixed electrode, the upper end of said member extending horizontally into the casing 29 through the end of the latter and co-operating with a fixed electrode 32 which is mounted on and extends through a partition 33 in the casing being connected with the adjacent end of the resistor 28. The partition 33 defines an auxiliary chamber 34 of comparatively small volume at the left hand end of the casing 29. This chamber is connected with the main space within the casing 6 by means of a pipe 35 so that pressure conditions within the unit 5 will be transmitted tojthe auxiliary chamber 34 and thereby to the gap between the electrodes 3i and 32. The pipe 35 preferably enters the casing 6 by means of a port 36 at a position subject to the drop in atmospheric pressure due to velocity of the gas discharging from the casing as will hereinafter be described in more detail.

The space with the tubular insulating casing 1 and a corresponding space within the assembly 2 is in communication. by way of the tubular insulator 3, with a control valve 37 arranged within the member 4. This control valve is normally biased on to its seating 38 by means of a compression spring 39. The space below the valve is connected by a pipe 40 with a source (not shown) of compressed air or gas. The valve 37 includes a stem 41 extending in airtight manner through the end cover 42 of the member 4 which stem is connected with suitable operating mechanism adapted to open said valve when the circuit breaker is to be opened such as in response to tripping mechanism for said circuit breaker. Since such operating mechanism for the valve is well known in the art. further description thereof is deemed unnecessary herein.

The contact unit 5 is provided with a terminal member 43 adapted to be connected with one supply line and a second terminal member 44 is carried by the member 16 for connection with the other supply 'line. As hereinbefore indicated, circuit-breakers of the kind described are usually employed in conjunction with an isolator switch such as in the manner shown in Fig. 2, wherein the terminal 44 constitutes a fixed contact adapted to be engaged by an isolator blade 45 which is movable into and out of engagement with the contact 44. In the example shown in Fig. 2 the blade 45 is fixedly mounted on the upper end of an insulating pillar 46 mounted for rotation about its vertical axis on a member 4, the blade 45 having electrical contact with a terminal member 44' adapted to be connected with the second mentioned supply line and having a pivotal connection at 47 with the blade 45 so as to permit the rotational movement of the latter, whilst the blade 44 remains fixed in space. Member 4 together with the member 4 are mounted for example on a fixed framework 48. The general arrangement of circuit-breaker shown in Fig. 2 is in itself well known to those skilled in the art, and it is therefore deemed unnecessary herein to describe the operating mechanism in detail. It is sulficient to state that an air operated servomotor or other means are provided for rotating the insulating pillar 46, the control means for this servomotor or means being suitably combined with that for the control valve 41 so that after the latter has been opened the isolator 45 will be moved out of engagement with the contact 44 so that the contacts within the member 1 may hen be reclosed by closure of the control valve 37.

It will be understood that the arrangement of Fig. 1 is, however, not limited to the general arrangement of circuit breaker described with reference to Fig. 2, but has general application.

In the operation of the arrangement shown in Fig. 1, during the normal closed condition of the contacts 11 and 14 the control valve 37 is closed so that the spring 18 urges the contact 11 into engagement with the contact 14 and the piston 23 occupies its uppermost position under the influence of the spring 24. In order to open the circuit the control valve 37 is opened so as to apply air pressure to the space within the member 1. This air pressure will urge the contact 11 away from the contact 14. The pressure air will then flow across the gap between the contacts into the contact 11 and flows from the latter into the casing 6 by way of ports such as 11a in the moving contact. This operation occurs so soon as the contact 11 leaves the contact 14, so that air pressure builds up within the casing 6 and, the spring 24, being of insuflicient strength to resist said pressure, the piston 23 is moved downwardly to its illustrated position thereby to allow escape of the air from the casing 6 to atmosphere by way of the ports 22. The flow of air thus extinguishes the are drawn between the contacts. Under normal conditions of recovery the voltage gap between the contacts 31 and 32 will break down so that the resistor becomes connected effectively in parallel with the open main contacts 11 and 14. The-breakdown of this gap may be facilitated by the connection of the auxiliary chamber 34 with the port 36, since the position of such port is such that due to the increased velocity of flow of the air from the casing 6 through the comparatively restricted upper end of the cylinder 21, namely above the shoulder 25, there will be a drop in static pressure which will be transmitted to the chamber 34.

The movement of the moving contact 11 to the illustrated fully open position results in the port 27 being uncovered by the piston 13, so that air pressure is applied through the pipe 26 to the underside of the piston 23. As a result, after a predetermined time interval dependent on the operating air pressure within the member 1 and on the dimensions of the pipe 26, the pressure below the piston 23 will build up to that above said piston and the latter will be returned to its original position so as to close the dischange ports 22. The pressure in the casing 6 then also builds up to that on the upstream side of the main contacts and is finallyapp'lied by means of the pipe 35 also to the auxiliary chamber 34. The space between the electrodes 31 and 32 is such in relation -to said pressure that at the normal line voltage the are will not be maintained between said electrodes, and the current in the resistor 28 will also be interrupted. Circuit interruption is thus completed and is maintained for so long as the control valve 37 remains open and pressure is thereby maintained in the contact chamber. The contacts 43 and 44 may therefore be connected with the respective line conductors, although isolating switches separate from the circuit interrupter itself will then usually be provided on one or both sides of the interrupter for permitting attention to the latter when required. In order to reclose the circuit the valve 37 is closed and an exhaust valve, the head of which appears at 37a is opened to connect the contact chamber with atmosphere.

If the circuit interrupter includes a series isolator as part thereof, such as in the arrangement of Fig. 2 for example, means responsive to the opening of the isolator may be arranged also to open the exhaust valve whereby to release the air or gas pressure maintained at this stage within the contact unit. The main contacts 11 and 14 of Fig. 1 will then reclose.

It will be understood that automatic reclosing operation can be provided by the usual means which, however, in application to the arrangement above described will be arranged to rlease the air pressure from the contact unit, namely by opening suitable exhaust valve means, as well as by closing the main air or gas control valve.

Fig. 3 illustrates a circuit-breaker arrangement wherein two contact units 5A and 5B are mounted respectively on tubular insulating members 1A and 1B extending oppositely from a common conductive assembly 2 and supported therefrom on a common vertical insulating member 3. Resistors are provided at 28A and 28B in parallel with the contacts in the two units 5A and 5B respectively, the electrodes 31A and 32A extending into the two auxiliary chambers respectively and the latter being connected respectively with the associated casings of the units 5A and 5B by means of pipes 35A and 35B. In this arrangement the assembly 2 is modified by the omission of the end cover 16, the contact 14 of Fig. 1 being duplicated within the tubular member 1B and the two fixed contacts being suitably supported such as by a spider member within the assembly 2.

Line terminals 43 and 44 are mounted respectively on the two units 5A and 5B, being for example connected with the line conductors directly or by means of a separate isolator switch or switches, or one terminal constituting a fixed contact of an isolator switch such as in the ar rangement of Fig. 2.

What we claim is:

1. A gas blast electric circuit interrupter comprising in combination, main circuit interrupting contacts, a resistor and a pair of fixed electrodes connected in series with one another in a circuit in parallel with said main contacts, said electrodes being separated by a gap which breaks down and permits passage of current through the resistor on opening of said main contacts, a closed pressure retaining chamber surrounding both said electrodes, and valve means controlling the flow of gas under pressure into said chamber, said valve means being operative on opening the circuit interrupter to increase the static pressure on said electrodes and the gap therebetween and quench the arc in the latter by said increase of static pressure and terminate the flow of current through said resistor.

2. A gas blast electric circuit interrupter comprising in combination, main circuit interrupting contacts, a resistor and a pair of fixed electrodes connected in series with one another in a circuit in parallel with said main contacts, said electrodes being separated by a gap which breaks down and permits passage of current through the resistor on opening of said main contacts, a closed pressure retaining chamber surrounding both said electrodes, valve means controlling flow of gas under pressure into said closed pressure retaining chamber, operating means for said main contacts and time delay means operative in response to said operating means to actuate said valve means to cause gas under pressure to flow into said chamber with a time delay after opening of said main contacts, whereby to increase the static pressure on said electrodes and the gap therebetween and quench the arc in the latter by said increase of static pressure and terminate the flow of current through said resistor.

3. A gas blast electric circuit interrupter comprising in combination, a main contact element, a co-operating main contact, a main contact chamber structure housing said contact element and said co-operating contact, a piston member connected with said contact element and displaceable within a cylinder by gas pressure within said main contact structure to move said contact element away from said co-operating contact, a resistor and a pair of fixed electrodes connected in series with one another in a circuit in parallel with said main contacts, said electrodes being separated by a gap which breaks down and permits passage of current through the resistor on opening of said main contacts, a closed pressure retaining chamber surrounding both said electrodes, valve means con trolling flow of gas under pressure into said closed pressure retaining chamber, pressure responsive operating means for said valve means, said operating means being connected with said main contact chamber structure to actuate said valve means to cause gas under pressure to flow into said chamber with a time delay after opening of said main contacts by the gas pressure within said main contact chamber structure, whereby to increase the static pressure on said electrodes and the gap therebetween and quench the arc in the latter by said increase of static pressure and terminate the flow of current through said resistor.

4. A gas blast electric circuit interrupter comprising in combination, main circuit interrupting contacts, a main contact chamber structure housing said main contacts and having gas outlet means on the downstream side of said main contacts, gas inlet means to said main contact chamher, a resistor and a pair of fixed electrodes connected in series with one another in a circuit in parallel with said main contacts, said electrodes being separated by a gap which breaks down and permits passage of current through the resistor on opening of said main contacts, a closed pressure retaining chamber surrounding both said electrodes, a passage connecting said closed pressure retaining chamber with the interior of said main contact chamber structure on the downstream side of said main contacts and on the upstream side of said gas outlet means, and valve means co-operating with said gas outlet means to close the latter in response to application of gas pressure to said main contact chamber, said valve means being thereby eifective to cause gas under pressure to flow into said closed pressure retaining chamber and increase the static pressure on said electrodes and the gap therebetween to the pressure on the upstream side of the main contacts and quench the arc in the latter by said increase of static pressure and terminate the flow of current through said resistor.

5. A gas blast electric circuit interrupter comprising in combination, a main contact element, a co-operating main contact, a main contact chamber structure housing said main contacts, gas inlet means to said main contact chamber structure, a first cylinder included in said main contact chamber structure, a first piston member connected with said contact element and displaceable within said first cylinder by gas pressure within said main contact chamber structure to move said contact element away from said co-operating contact, a resistor and a pair of fixed electrodes connected in series with one another in a circuit in parallel with said main contacts, said electrodes being separated by a gap which breaks down and permits passage of current through the resistor on opening of said main contacts, a closed pressure retaining chamber surrounding both said electrodes, a passage connecting said closed pressure retaining chamber with the interior of said main contact chamber structure on the downstream side of said main contacts, a second cylinder included in said main contact chamber structure and having at least one discharge port for said structure, a second piston movable within said second cylinder between a first position in which said port is open and a second position in which said piston closes said port, means connecting said second cylinder on the side of said second piston remote from said port with a port in said first cylinder closed when said contact element is in engagement with said co-operating contact and opened on separation of said contact element from said :contact to apply gas pressure to said second piston to close said first port in response to application of gas pressure to said main contact chamber, said second piston being thereby efiective to cause gas under pressure to flow into said closed pressure retaining chamber and increase the static pressure on said electrodes and the gap therebetween to the pressure on the upstream side of the main contacts and quench the arc in the latter by said increase of static pressure and terminate the flow of current through'said resistor.

References Cited in the file of this patent UNITED STATES PATENTS 10 2,391,826 Flurscheim Dec. 25, 1945 2,453,555 Thommen Nov. 9, 1948 2,581,822 Thommen et al. Jan. .8, 1952 2,596,254 Latour May 13, 1952 2,665,351 Forwald Jan. 5, 1954

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